A study conducted by the National Oceanic and Atmospheric Administration and the University of Washington has concluded that warmer sea and land temperatures along the Pacific coast in North America over the past 100 years are due to weak winds–and not due to human activities or “climate change.” The study was published Monday on the eve of the UN Climate Summit by Proceedings of the National Academy of Sciences.

The study, published as “Atmospheric controls on northeast Pacific temperature variability and change, 1900–2012,” reports that while “Northeast Pacific coastal warming since 1900 is often ascribed to anthropogenic greenhouse forcing…century-long warming around the northeast Pacific margins, like multidecadal variability, can be primarily attributed to changes in atmospheric circulation,” and not to human burning of fossil fuels.

The Los Angeles Timesquotes study leader James Johnstone: “Changing winds appear to explain a very large fraction of the warming from year to year, decade to decade and the long-term.” The Times adds: “This latest research shows that similar changes in atmospheric and ocean circulation can drive trends that last a century or longer, overshadowing the effects of human-generated increase in greenhouse gases, the study’s authors said.

By analyzing records of sea surface temperatures, sea level pressure, and land-based surface air temperatures, the study–which was reviewed for nearly a year before publication–demonstrates that natural changes in wind patterns “account for more than 80% of the 1900–2012 linear warming” and that “natural internally generated changes in atmospheric circulation were the primary cause of coastal NE Pacific warming from 1900 to 2012.”

On Tuesday, California’s Gov. Jerry Brown will address two panel discussions at the UN gathering. On Sunday, signing several laws aimed at reducing climate change, Brown said that “we know in California that carbon pollution kills, it undermines our environment, and, long-term, it’s an economic loser,” adding “We face an existential challenge with the changes in our climate. The time to act is now. The place to look is California.”

Brown has also blamed climate change for numerous weather-related phenomena in California, including warm temperatures, a severe drought, and wildfires. “There is no scientific question,” Brown said in May, accusing the Republican Party of denying the scientific evidence on climate change. The Governor’s Office of Planning and Research maintains a website devoted to refuting climate change “deniers” by referring to scientific data.